Scalable Link-Level Flow-Control for a Switching Device

1. A switching device for transporting packets of data, the packets being received at the switching device based on flow-control information, the device comprising a memory for storing the packets, a credit counter coupled to the memory for counting a credit number of packets departing from the memory, and a scheduler unit coupled to the credit counter for deriving the flow-control information in response to the credit number, where the memory is comprised of an N times M number of memory units arranged in an N switch row by M switch column matrix, where at least M is greater than one, where there are N times M credit counters individual ones of which are associated with an individual one of the N times M number of memory units, where the scheduler unit is comprised of N schedulers one for each of the N switch rows of memory units and coupled to each of M credit counters within the associated switch row of memory units, and where the flow-control information comprises N flow control signals individual ones of which are configured to specify for the storage of data one of the M memory units of an associated switch row of memory units.

2. The switching device according to claim 1 , further comprising an occupancy counter coupled to the memory for determining a packet occupancy level of the memory, where the packet occupancy level is usable by the scheduler unit for deriving the flow-control information in response to the credit number and the packet occupancy level.

3. The switching device according to claim 1 , wherein the scheduler unit comprises a credit-number-determination unit for determining the credit number of each memory unit within the switch row.

4. The switching device according to claim 3 , wherein the scheduler unit comprises an occupancy-determination unit for assessing the packet occupancy level of each memory unit within the switch row and further comprises reception means for receiving communication-device-input information which indicates a communication-device status, and wherein the scheduler unit further comprises a logic unit for determining the memory unit to which a further packet may be directed based on the determined credit numbers, the packet occupancy levels, and the communication-device-input information.

5. The switching device according to claim 1 , wherein the scheduler unit comprises an occupancy-determination unit for assessing the packet occupancy level of each memory unit within the switch row.

6. The switching device according to claim 1 , wherein the scheduler unit further comprises reception means for receiving communication-device-input information which indicates a communication-device status.

7. Switching apparatus comprising the switching device according to claim 1 and a communication device connected to the switching device.

8. A method for generating flow-control information comprising the steps of: storing packing of data in a memory that comprises memory unit, counting a credit number of packets departing from the memory, and deriving the flow-control information in response to the credit number, where the memory is comprised of an N times M number of memory units arranged in an N switch row by M switch column matrix, where at least Mis greater than one, where there are N times M credit counters individual ones of which are associated with an individual one of the N times M number of memory units, where the scheduler unit is comprised of N schedulers one for each of the N switch rows of memory units and coupled to each of M credit counters within the associated switch row of memory units, and where the flow-control information comprises N flow control signals individual ones of which are configured to specify for the storage of data one of the M memory units of an associated switch row of memory units.

9. The method according to claim 8 , further comprises determining a packet occupancy level of the memory and using the packet occupancy level in the step of deriving the flow-control information.

10. The method according to claim 9 , further comprises determining the packet occupancy level and the credit number of a plurality of the memory units.

11. The method according to claim 8 , further comprises receiving from a communication device communication-device-input information that indicates a communication-device status.

12. The method according to claim 11 , wherein the communication-device-input information is used in the step of deriving the flow-control information.

13. The method according to claim 8 , further comprising: determining a packet occupancy level of the memory; receiving from a communication device communication-device-input information that indecates a communication-device status; and wherein the step of deriving the flow-control information further comprising determining a memory unit to which a further packet may be directed based on the determined packet occupancy level, the credit number, and the communication-device-input information.

14. The method according to claim 8 , further comprising prioritizing credits using a highest memory occupancy first (HMF) procedure intended to maintain as active existing flows.

15. The method according to claim 8 , further comprising prioritizing credits using a highest memory vacancy first (HYF) procedure intended to support flows that make forward progress at the switch level.

16. A switching device, comprising: an input for receiving a flow of data packets, the data packets being received based on flow control information; and a memory for storing received data packets, the memory comprised of at least one row of individually addressable memory units, each memory unit having associated therewith a credit counter and the at least one row of memory units having associated therewith a reception scheduler having inputs coupled to outputs of the credit counters, said reception scheduler having an output providing the flow control information based at least on the outputs of the credit counters, where credits are prioritized using one of a highest memory occupancy first (HMF) procedure intended to maintain as active existing flows or by using a highest memory vacancy first (HVF) procedure intended to support flows that make forward progress at the switch level.

17. The switching device of claim 16 , further comprising a memory occupancy counter having an output coupled to said reception scheduler, where the flow control information is also based on the memory occupancy counter, and where the flow control information comprises information to specify a memory unit to store a data packet.